1887

Abstract

The activity of glutamate dehydrogenase (NADP) (EC 1.4.1.4; NADP-GDH) of is decreased under conditions in which intracellular ammonia concentration increases. A high internal ammonia concentration can be obtained () by increasing the ammonium sulphate concentration in the culture medium, and () by growing the yeast either in acetate + ammonia media, where the pH of the medium rises during growth, or in heavily buffered glucose + ammonia media at pH 7.5. Under these conditions cellular oxoglutarate concentrations do not vary and changes in NADP-GDH activity appear to provide a constant rate of oxoglutarate utilization. The following results suggest that the decrease in NADP-GDH activity in ammonia-accumulating yeast cells is brought about by repression of synthesis: (i) after a shift to high ammonium sulphate concentrations, the number of units of activity per cell decreased as the inverse of cell doubling; and (ii) the rate of degradation of labelled NADP-GDH was essentially the same in ammonia-accumulating yeast cells and in controls, whereas the synthesis constant was much lower in the ammonia-accumulating cells than in the controls.

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/content/journal/micro/10.1099/00221287-131-6-1425
1985-06-01
2019-10-20
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http://instance.metastore.ingenta.com/content/journal/micro/10.1099/00221287-131-6-1425
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